Centennial climate variability over the last ice age exhibits clear bipolar behavior. High-resolution analyses of marine sediment cores from the Iberian margin trace a number of associated changes simultaneously. Proxies of sea surface temperature and water mass distribution, as well as relative biomarker content, demonstrate that this typical north-south coupling was pervasive for the cold phases of climate during the past 420,000 years. Cold episodes after relatively warm and largely ice-free periods occurred when the predominance of deep water formation changed from northern to southern sources. These results reinforce the connection between rapid climate changes at Mediterranean latitudes and century-to-millennial variability in northern and southern polar regions.

Supplement to: Martrat, Belén; Grimalt, Joan O; Shackleton, Nicholas J; de Abreu, Lucia; Hutterli, Manuel A; Stocker, Thomas F (2007): Four climate cycles of recurring deep and surface water destabilizations on the Iberian Margin. Science, 317(5837), 502-507